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arXiv · 1509.07878

Outer-disk reddening and gas-phase metallicities: The CALIFA connection

R. A. Marino·A. Gil de Paz·S. F. Sánchez·P. Sánchez-Blazquez·N. Cardiel·A. Castillo-Morales·S. Pascual·J. Vílchez·C. Kehrig·M. Mollá·J. Mendez-Abreu·C. Catalán-Torrecilla·E. Florido·I. Perez·T. Ruiz-Lara·S. Ellis·A. R. López-Sánchez·R. M. González Delgado·A. de Lorenzo-Cáceres·R. García-Benito·L. Galbany·S. Zibetti·C. Cortijo·V. Kalinova·D. Mast·J. Iglesias-Páramo·P. Papaderos·C. J. Walcher·J. Bland-Hawthorn·the CALIFA Team
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Abstract

We study, for the first time in a statistically significant and well-defined sample, the relation between the outer-disk ionized-gas metallicity gradients and the presence of breaks in the surface brightness profiles of disk galaxies. SDSS g'- and r'-band surface brightness, (g'- r') color, and ionized-gas oxygen abundance profiles for 324 galaxies within the CALIFA survey are used for this purpose. We perform a detailed light-profile classification finding that 84% of our disks show down- or up-bending profiles (Type II and Type III, respectively) while the remaining 16% are well fitted by one single exponential (Type I). The analysis of the color gradients at both sides of this break shows a U-shaped profile for most Type II galaxies with an average minimum (g'- r') color of ~0.5 mag and a ionized-gas metallicity flattening associated to it only in the case of low-mass galaxies. More massive systems show a rather uniform negative metallicity gradient. The correlation between metallicity flattening and stellar mass results in p-values as low as 0.01. Independently of the mechanism having shaped the outer light profiles of these galaxies, stellar migration or a previous episode of star formation in a shrinking star-forming disk, it is clear that the imprint in their ionized-gas metallicity was different for low- and high-mass Type II galaxies. In the case of Type III disks, a positive correlation between the change in color and abundance gradient is found (the null hypothesis is ruled out with a p-value of 0.02), with the outer disks of Type III galaxies with masses $\leq$10$^{10}$ M$_{\odot}$ showing a weak color reddening or even a bluing. This is interpreted as primarily due to a mass down-sizing effect on the population of Type III galaxies having recently experienced an enhanced inside-out growth.

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R. A. Marino, A. Gil de Paz, S. F. Sánchez, P. Sánchez-Blazquez, N. Cardiel, A. Castillo-Morales, S. Pascual, J. Vílchez, C. Kehrig, M. Mollá, J. Mendez-Abreu, C. Catalán-Torrecilla, E. Florido, I. Perez, T. Ruiz-Lara, S. Ellis, A. R. López-Sánchez, R. M. González Delgado, A. de Lorenzo-Cáceres, R. García-Benito, L. Galbany, S. Zibetti, C. Cortijo, V. Kalinova, D. Mast, J. Iglesias-Páramo, P. Papaderos, C. J. Walcher, J. Bland-Hawthorn, the CALIFA Team. 2015-09-25. Outer-disk reddening and gas-phase metallicities: The CALIFA connection. https://doi.org/10.1051/0004-6361%2F201526986

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